Spark Plugs: NGK vs. Denso vs. Bosch

Let's talk spark plugs. I'm about ready to replace my NGK Platinums and I have been researching plugs the last two days. I have been looking into NGK Platinums, Denso Iridium and Bosch Platinum. I found two very interesing dyno runs comparing the Denso Iridium Race plugs VS Bosch Platinum ( http://www.importreview.com/reviews/densoVSbosch.html ) and Bosch Platiunum VS NGK V-Power ( http://www.importreview.com/reviews/BoschVSNGK.html ). And in both dyno runs on a Honda D16 the standard Bosch Platinum plugs (not Platinum+4) did extremely well.

I ran Bosch Platinum plugs in my previous Honda ('86 CRX Si) and I was very pleased with the performance. The NGK and the Denso plugs run around $14 a plug whereas the standard Bosch Platinums run $2 a plug and the Bosch Platinum+4 run $6 a plug. So I'm kind of leaning towards the Bosch plugs (standard Platinum or Platinum+4).

If your motor is internally stock, then there is no real reason to use any other plug. Granted, if you're boosting of on nitrous, of course..
but Honda designed a particular spark plug to work with a particular engine. They took into account the combustion chamber shape, piston dome or dish, flame travel, etc.

I was in the same boat as you recently... I wanted to try the Bosch Plat +4 but the Bosch reference indicated I should use the +2 in the ITR. I've had them in the car for about a month now and I am very happy. There was a small improvement in the torque feel of the car .. it seems to pull stronger. I did notice a little bit of bad idle when I first installed the plugs but it went away after about 5 minutes of normal driving. I liked these plugs so much that I bought the +4 for my Mazda 323

Mike, I would generally agree with you comment. But in this instance it is hard to dispute the facts. Now don't get me wrong, I'm not putting down NGK.

I have been running NGKs for 60k miles and I don't have one bad thing to say about them. Actually, my car came with Denso plugs standard (not NGK). I had read a few comments from people that they "felt" that NGK plugs were better than Denso. So at 15k miles, I replaced the Densos with NGKs and I really didn't notice any difference. So now I have almost 75k miles and it about time to replace the plugs. I still have the Denso, so I could replace the worn NGKs with them. Or I could replace the worn NGKs with a new set of NGKs. Or I could give the Bosch Platinums (standard or +4) a try. I still haven't made up my mind. That's why I'm looking for some feedback.

I noticed that the Type-R uses a different NGK plug (PFR6G-11) than the GS-R. I looked into see what the difference was and found out that the only difference is the plug gap. The PFR6G-13 has a spark gap of 1.3mm (.052") and the PFR6G-11 has a spark gap of 1.1mm (.044"). This made me wonder why there would be a different gap. I was going to ask this question, but I actually found the answer on NGK's website ( http://www.ngksparkplugs.com/techinf.../faqpregap.asp )and I thought that I would share the info. Here is the explanation:

Another consideration that should be taken into account is the extent of any modifications that you may have made to the engine. As an example, when you raise compression or add forced induction (a turbo system, nitrous or supercharger kit) you must reduce the gap (about .004" for every 50 hp you add). However, when you add a high power ignition system (such as those offered by MSD, Crane, Nology) you can open the gap from .002-.005".

One other piece of information that I found interesting was when I was looking up the plug number for my car on Denso's website ( http://www.densoiridium.com/findmypart.asp ). The GS-R and the Type-R use the same plug number (IK-20) for all years. Also for years '94-'99 they use the same plug gap (.044"). But for years '00-'01 the GS-R uses (.050") and the Type-R still uses (.044"). I'm not really sure for this difference.

It is important to remember that spark plugs do not create heat, they can only remove heat. The spark plug works as a heat exchanger by pulling unwanted thermal energy away from the combustion chamber, and transferring the heat to the engine's cooling system. The heat range is defined as a plug's ability to dissipate heat.

I recommend NGK BKR6E-11 copper plugs for GS-R's, changing them every 10K-15K miles. At under $9 for a set of 4, you can beat it (conducts better than platinum or iridium, only takes 5 minutes to change).